Field Notes

Twitchell Alfalfa: 2013-06-13 14:30:00 (DOY 164)
Author: Cove Sturtevant
Others: Laurie, Yanel

Summary: Alfalfa very flowery. Placed spines on top of sonic and 7500. Something wrong with longwave radiation readings, will investigate further. Resealed camera box glass.

Twitchell Alfalfa
2013-06-13

We arrived at approximately 14:30 PDT. It was sunny and warm/hot with a mild breeze. The alfalfa was much more flowery this week, above knee height with multiple layers of flowers and constant buzzing of insects. The sonic was again covered in birdie doo (and from the looks of the ground under the sensors there was a doodoo party before we got there). We were prepared this time with spines for the sonic and 7500, which Laurie and Yanel attached after carefully cleaning the transducers. The sonic had to be taken down to do this, and was realigned with true north afterward.

I downloaded data and checked the sensor readings. All flux data looked good but there is something funky with the longwave radiation readings. The radiation boom was set up with the same NR01 and CNR1 instruments and program I used to test the instruments at the lab (which went great), but the longwave channels on both instruments are reading too high in the field. The outgoing longwave channel on the CNR1 was reading about 7 mV, which when accounting for the 30 C instrument temperature indicated a ground temperature of over 100 C. Clearly not right. In addition, incoming longwave channels were reading about the same positive voltage as the outgoing channels, which is really not right given the clear sky. All connections looked good and the program did as well. The sensor readings responded correctly when I put my hand over them, so Im not sure the problem. I brought back the CNR1 to recreate the setup in the lab, check the data, and test further.

7500 readings:
CO2 = 394 ppm (same after cleaning)
H2O = 515 mmol m-3 (same after cleaning)
SS = 91.9% (93.5% after cleaning)
p = 101.7 kPa
sos = 350 m s-1

MET looked good. 7550 clock was correct. Yanel and I resealed the camera box glass. Yanel and Laurie tested Joes new LED NDVI sensor over the alfalfa. Yanel cleaned the solar panels.

0 photos found

7 sets found

Can't check TA_met
11 TA_met graphs found